Daniel,
I've been experimenting with ways to scratchbuild trees. . .and this is what I've come up with so far. Using floral wire and tape, I cut 20-30 strands of wire to size, wrap them with the tape, shape it into something that sort of looks like a tree, then brush it with thin plaster to hide the wire. Once the plaster dries, I'll paint it with tie brown or some other grey-ish brown color. Once that dries, I'll coat the ends of the branches with clear caulk, then apply WS underbrush to the branch ends. The pictures below kind of detail the process.
I'm not thrilled with the WS underbrush, and want to experiment with other foliage products for a more realistic look, but this works for me pretty welll. I think the underbrush is too thick, and I'm looking for a lighter, translucent look.
I build 5-6 trees at a time, do all the wire and plaster, then the paint, and finally, the foliage, so it's broken down into 3 separate sessions. I've found that if I do more than 5-6 at a time, my work gets pretty lousy.
After reading your post, I've done the wire work for an eastern white pine. I think this method might work, perhaps not as a display specimen model, but to fill in the forests and give the viewer the general look of a pine forest. Let me know what you think of this. If you're interested, I can post pictures of the pine in progress.
On the plus side, this method is DIRT CHEAP, and a nice change of pace from other MR projects. It takes some time, but it's not too draining because it's broken down into three 30-45 minute sessions.
Kevin